Znorg. Chem. 1993,32, 5119-5125
5119
Synthesis, Characterization, and Reactions of Platinum and Rhodium Complexes of the Hybrid Phosphorus-Nitrogen Ligand 4-CH3C&C[N(SiMe3)]( NPPh2): X-ray Structures of [Mh(PPh2NHC(4-CH3C&)NH)]X (M = Pt, X = C1; M = Rh, X = BF4) Tristram Chivers,' Katherine MeGregor, and Masood Parvez Department of Chemistry, The University of Calgary, 2500 University Drive N.W., Calgary, Alberta T2N 1N4, Canada
Received May 13, 1993. The reactionof 4-CH3C6H4C[N(SiMe3)2](NPPh2) with [Pt(PEt3)C12]2or [Rh(cod)Cl]2in a 2:l molar ratioin T H F (4a)and Rh(cod) [PPhlproduces the monodentate complexes trans-Pt(PEt3) [PP~~NC(~-CH~C~H~)N(S~M~~)~]C~Z NC(4-CH3C6H,)N(SiMe3)2]Cl (4b), which were characterized by lH and 31PNMR spectroscopy. The reaction of 4a with PhSeCl in a 1:2molar ratio yields Pt(PEt,)Cl[PPh2NHC(4-CHpC6H4)NH]Cl(5), which was identified by lH and ,lP NMR spectroscopy and by X-ray crystallography. This complex crytallizes in the space group Pi with a = 11.840(1) A, b = 14.523(8) A, c = 10.081(3) A, a = 107.93(3)', /3 = 90.00(2)O, y = 87.60(2)O,Z = 2,and R = 0.044 for 2950observed reflections. The PPh2NHC(4-CH3CsH4)NH ligand in 5 is chelatedvia phosphorus and nitrogen to platinum with the PPh2 and PEt3 groups in cis positions and hydrogen-bonding [d(H(N)-Cl) = 2.20 A] between the N H group attached to phosphorus and the chloride counterion. By contrast, the 1H-15N HMQC spectra of 5 indicate that in solution the other N H group (a(lH) = 12.73 ppm) is involved in strong hydrogen-bonding with the chloride counterion. The decomposition of 4a in boiling T H F also yields 5. Possible pathwaysfor the formationof5 by thesetwodifferent routes arediscussad. Thereaction o ~ ~ - C H ~ C ~ H , C [ N ( S ~ M ~ ~ ) ~ ] (NPPh2) with [Rh(cod)Cl]~in acetone in the presence of NaBF4 produces [ R ~ ( c o ~ ) ( P P ~ ~ N H C ( ~ - C H ~ C ~ H , ) NH)]BF4 (8), which was characterized by lH and 31PNMR spectra and by X-ray crystallography. The crystals of 8 are triclinic, space group Pi,with a = 13.844(6) A, b = 14.236(7) A, c = 9.156(5) A, a = 99.08(4)O, /3 = 105.08(4)O,y = 68.84(3)O Z - 2,and R = 0.074for 2929 observed reflections. The PPh2NHC(4-CH3C6H,)NH ligand in 8 is chelated to rhodium in a fashion similar to that observed for 5. The reaction of 4-CH3C&C[N(SiMe3)2](NPPhz)with [Rh(C0)2C1]2 in a 2:l molar ratio in T H F produces Rh(CO)[PPhzNHC(4-CH&sH,)NHIC1 identified by lH, 13C, and 31P NMR and IR spectroscopic data.
Introduction Recently we reported the unexpected formation of the resonance-stabilized radicals ArCN2(EPh)$ (Ar = aryl; E = S,Se), la.' These radicals are generated by the reaction of ArPh
la E=E'=S,,Sa lb E = pph, E = S, Sa
its reactions with transitions metals.3 This paper describes some coordination chemistry of the N-(diphenylphosphino-N',N'-bis(trimethylsily1)benzamidineligand 3c with the platinum group metals, and the results of our efforts to generate complexes of the type 2b.
Experimental Section
2. E=E'=S,*Se
30 E = S , S e
2b E =PpzI. E = S, Se
2~ ~ ~ , ' ~ ~ & 3 c
[N(SiMe3)2] [NSiMe3] with PhECl in a 1:3 molar ratio and are remarkably persistent at room temperature, but nitrogen-centered dimerization occurs within several hours to give the diazenes trawArENC(Ph)N=NC(Ph)NEAr.' However, preliminary attempts to trap la as the corresponding metal complexes 2a, e.g. by generationof l a in thepresenctofPtCl~(PhCN)2or[Rh(C0)2C1]2, were unsuccessful. Consequently, we adopted an alternative strategy involving the coordination of the ligands 3alb to a metal prior to radical formation. The preparation of such metal complexes did not procced cleanly, so we turned our attention to the generation of the related hybrid radical ArCN2(PPh2)(E'Ph) (lb) as the corresponding metal complexes 2b. The synthesis of the ligand 3b was first reported by Roesky and co-workers2 in 1988;however, only one report had since appeared concerning Abstract publiihed in Advance ACS Abstracts, October 15, 1993. (1) (a) Chandraackhar, V.;Chivers,T.; Fait, J. F.; Kumarave1.S. S.J.Am. Chrm. Soc. 1990, 112, 5374. (b) Chandrasekhar, V.; Chivers, T.; Kumaravel, S.S.;Parvez, M.; Rao, M.N. S . Inorg. Chrm. 1991, 30, 4125.
0020-1669193/ 1 332-5 1 19$04.00/0
Reagents and General Procedures. All reactions and manipulations were performed under an atmosphere of dry argon gas using standard Schlenk techniques. All solvents were dried and distilled before use: THF, hexanes, diethyl ether (sodium benzophenone), CHzClz (PzOs), 6 and H sacetone (CaHz). The compounds [PtClz(PEt3)]~,4[Rh(cod)Cl]~? and PhSC16 were prepared according to the published procedure. [Rh(C0)2C1]2, n-BuLi, HN(SiMe3)z. 4-CH3C,jH&N, chlorodiphenylphosphine, and PhSeCl (Aldrich) wereuscd as received. Theelemental analyses were performed by the microanalytical service within the Chemistry Department at The University of Calgary. Iastrumentrtioa. Infrared spectra were recorded as solutions (KBr solution cell) or Nujol mulls (KBr plates) on a Nicolet DX-5 FTIR spectrometer. 31P(lH)NMR spectra were recorded on a Bruker AM400 spectrometer operating at 161.978 MHz in THF. A D20 insert was used as the lock for the phosphorus-31 spectra. Routine proton and carbon-13 NMR spectra were run on a Bruker AC-200 at 200.132 and 50.323 MHz, respectively. The solvent deuterium resonance served as the lock for both nuclei. Phosphorus-31 chemical shifts are reported in ppm relative to 85% H3PO4; proton and carbon-13 chemical shifts are reported in ppm relative to the residual protonated solvent. The 2D (2) (a) Scholz, U.; Noltemeyer, M.;Rosesky, H.W. Z. 2. Naturforsch.
1988,138,937. (b) Chandrasekhar,V.; Chivers, T.; Kumaravel, S.S.;
Meet", A.; van de Grampel, J. C. Inorg. Chrm. 1991,30, 3402. (3) Red, R. W.Ph.D. Thesis, University of Alberta, 1991. (4) Chatt, J.; Venanzi, L. J. Chrm. Soc. 1955,2787. ( 5 ) Giordano, G.; Crabtree, R. H. Inorg. Synth. 1919, 19, 218. ( 6 ) Mueller, W. H. J. J. Am. Chrm. Soc. 1968, 90,2075. 0 1993 American Chemical Society
5120 Inorganic Chemistry, Vol. 32, No. 23, 1993
Chivers et al.
Table I. Crystallographic Data for IH-IsN HMQC7 (heteronuclear multiple quantum coherence) spectra C~~-[P~(PE~~)(PP~~NHC(~-CH~C~H~)NH)CI]CI.THF (STHF) and were obtained on a Bruker AMX-500 spectrometer as described [R~(~~~)(PP~~NHC(~-CH~C~HI)NH)]BFC(CH~)~CO previously.8 A standard four-pulse-HMQC sequence was used.' The (WCWzCO) ISN-decoupledHMQC spectra were acquired using GARP. The proton and nitrogen resonance frequencies were 500.139 and 50.693 MHz, formula C ~ O H ~ ~ N ~ O P ) ~C C ~I ~I P H ~~ ~ B F ~ N ~ O P ~ R ~ respectively. Chemical shiftswere referenced tointernal tetramethylsilane fw 774.62 674.33 (IH) and external nitromethane (lsN). space group Pi P1 11.840(1) 13.844(6) P n p m t i ~ ~(a) . 4-CH&WN(SiMe3)2INPPb21 (3c). HNa, A 14.523(8) 14.236(7) b, A (SiMe3)z (20.8 mL, 0.1 mol) in Et20 (50 mL) was added dropwise at 10.08l(3) 9.156(5) C, A 0 OC to a solution of n-BuLi (40 mL of a 2.5 M solution in hexanes, 0.1 107.93(3) 99.08(4) a,deg mol) in 100 mL of EtzO. The solution was allowed to warm to room 90.00(2) 105.08(4) 6, deg temperature and stirred for 30 min. 4-CH3CsH4CN (12.0 mL, 0.1 mol) 87.60(2) 68.84(3) was added dropwiseto the above solution of LiN(SiMe3)z. The reaction 1647.7(9) 1620(1) mixture was stirred for 2 h at ambient temperature and then cooled to 23 -103 -78 OC. Chlorodiphenylphosphine (22.1 g, 18.0 mL, 0.1 mol) in THF 0.710 69 0.710 69 (50 mL) was added dropwise, and the reaction mixture was stirred and 1.807 1.382 allowed to warm to room temperature. The solvent was removed under 4.525 0.624 vacuum, the residue was extracted with CHzClz (50 mL), and the extract 0.044 0.074 was filtered through Celite to remove LiCI. The filtrate was evaporated 0.045 0.082 to drynea and the residue recrystallized from CHzClZ/hexanes (15) IFJI/ZIFd. Rw = [ ~ W C P / C W F ~ ~ ] ~ / ~ . giving k as a yellow solid in 75%yield. Anal. Calcd for C26H3sN2PSi2: C,67.49;H,7.62;N,6.06. Found: C,67.37;H,7.31;N,5.95. IHNMR (CDCI3): 0.13 (s, Me&, 18H), 2.39 (s, CHsC6H4, 3H), 7.13-7.66 (m, 11 H), 4.16 (s, br, olefinic cod CH, 2H), 5.91 (s, br, olefinic CH, 2H), C a s and CHsC&, 14H). 7.36-7.89 (m, C a s and CH3C&, 14H), 8.65 (s, br, NH, l.IH), 9.12 (s, br, NH, 0.7H). (b) ~~~P~(PE~~)(PP~I~NC(~-CH=)N(S~M~~)~)CI~ (44. A solution of 3c (0.12 g, 0.26 mmol) in THF (20 mL) was added dropwise (f) R h ( C O ) ( P W m C ( 4 ) ~ ) C I ( 8 ) Asolutionofk(0.24 . to a THF (or CH2Cl2) solution (20 mL) of [Pt(PEt3)Cl2]2 (0.10 g, 0.13 g, 0.514 mmol) in THF (20 mL) was added dropwise to a THF solution mmol) at 0 OC. The resultant pale yellow solution was allowed to warm (l5mL)of [Rh(C0)2C1]2(0.10g,0.257mmol)at-78OC. Thesolution to ambient temperature and stirred for 1 h. The solvent was evaporated was allowed to warm to room temperature, stirred for 30 min, and reduced to dryness and the pale yellow residue recrystallized from THF/pentane in volume to approximately 10 mL. Upon continued stirring under a at -18 OC; yield 62%. Anal. Calcd for C~~HNNZCIZPZP~S~Z: C, 45.38; steady stream of argon gas, a pale yellow precipitate was isolated from H, 5.95; N, 3.31. Found: C, 44.29; H, 5.88; N, 3.26. IH NMR the solution, giving 8.THF in 45% yield. Anal. Calcd for (CDCl3): 0.15 (s, Me&, 18H), 1.16 (dt, PCH2CH3, 9H), 1.81 (m, C2~H27N202PRhCl:C, 53.93; H, 4.89; N, 5.03. Found: C, 53.11; H, PCHzCH3, 6H), 2.31 (s, CH&H4, 3H), 7.00-7.75 (m, C& and 4.82; N, 5.04. IR (CH2C12 solution): YCO 1991 cm-I. IR (Nujol): v a C H s C a , 14H). 1979cm-';y~~3279,3172cm-'.'HNMR(CDCI3): 2.34(s,CH&,jHd, (c) Rh(cod) (PPhflC( 4-CH&&)N( SiMe3)2)CI (4b). This was 3H),6.80(s,NH, lH),7.19-7.886(m,NH,C,$isandCH$fi,15H). prepared in THF (or CH2C12) by using a proccdure similar to that I3CNMR (CDCla): 189.4 (dd, CO, 'J(Rh-C) = 68 Hz, 'J(C-P) * 17 described for the synthesis of 4a. The residue was recrystallized from Hz) . CH,CN, giving 4b as an orange microcrystallineproduct in 45% yield. X-ray Analyses. (a) 5. A suitable colorless crystal of cis-[PtAnal. Calcd for C32H47N2CIPRhSi2: C, 57.58; H, 6.68; N, 3.95. (PEt3)CI(PPhzNHC(C&I&H3)NH)]Cl.THF (STHF) was obtainedby Found: C, 56.32; H, 6.42; N, 3.92. IH NMR (CDCl3): 0.15 (s, Me&, recrystallization from THF at ambient temperature. Accurate cell 18H), 2.30 (m, CH,C&i4 and aliphatic cod CH2, 11H), 3.50 (s, br, dimensionsand a crystal orientation matrix were determinedon a Rigaku olefinic cod CH, 2H), 5.40 (s, br, olefinic cod CH, 2H), 7.24-7.71 (m, AFC6S diffractometer by a least-squares fit of the setting angles of 15 CsHs and CH,C&, 14H). reflections with 28 in the range 20-25'. Intensity data were collected (a) C~~[P~(PE~~)CI(PP~~C(C&CH~)NH))CI (5). A solution of by the 0/28 method using a scan speed of 4.0°/min, scan width of (1.05 3c (0.12 g, 0.26 mmol) in THF (20 mL) was added dropwise to a THF + 0.35 tan 8 ) O , and monochromatized Mo KCYradiation in the range 2 solution (20 mL) of [Pt(PEt,)C12]2 (0.10 g, 0.13 mmol) at 0 OC. The
